Villain(s)  Scientist effected with radiation

Actor(s):  Robert Clarke, Patricia Manning, Nan Peterson, Patrick Whyte

Brief Description  The Hideous Sun Demon (1958) is an independent American science fiction horror film about an atomic research scientist who transformed into a murderous, lizard-like creature whenever he was exposed to direct sunlight. Produced, directed, and co-written by Robert Clarke—who also starred in the title role—the low-budget creature feature has since become a cult classic of 1950s "so bad it's good" B-movie cinema.

Plot:
Research scientist Dr. Gilbert "Gil" McKenna is accidentally exposed to a near-fatal dose of a newly discovered radioactive cosmic isotope at a nuclear test lab. Doctors are baffled when Gil shows no immediate radiation burns. However, while recovering on a hospital sun deck, solar radiation triggers a horrifying genetic reversal, devolving him into a scaly, reptilian monster. Gil learns that the transformation reverses itself after a few hours spent in total darkness, but subsequent exposures cause the mutation to occur faster and last longer.

Stricken with dread and ordered to stay indoors, Gil falls into deep depression and alcoholism. He retreats to a darkened house, fiercely protected by his loyal assistant and unrequited love, Ann Russell. Seeking escape, Gil slips out at night to a local bar, where he begins a brief fling with Trudy, a nightclub singer. This draws the wrath of Trudy's gangster boyfriend. Following a confrontation where Gil transforms in the sun and kills the mobster, he goes on the lam from local police. The pursuit culminates in a dramatic showdown on top of a high industrial tower, ending in his fatal fall.